Application of Fe–Cr alloys to solid oxide fuel cells for cost-reduction: Oxidation behavior of alloys in methane fuel

Oxide scale formations in anode gas atmospheres were investigated for three different Fe–Cr alloys as interconnects in solid oxide fuel cells (ZMG232, SUS430, and Fe–Cr–W). Oxidation with anode gases (CH4, H2O, CO, and CO2) caused a relatively thick oxide scale formation on the alloy surfaces even in low oxygen partial pressures at 1073 K. The distribution of elements in the oxide scale and the growth rates of oxide scales were compared among the examined alloys by glow discharge optical emission spectrometry (GDOES). Mn–Fe–Cr spinels and Cr2O3 were formed on ZMG232 and SUS430 surfaces, whereas only Cr2O3 formation was observed on Fe–Cr–W surface. Oxide scale thickness grew with annealing time by a parabolic relationship, and the growth rates were in the orders of 10−6 to 10−5 μm2 s−1 at 1073 K. The electrical conductivity after forming oxide scales was different depending on the oxide scale phases and thickness. The conductivity was in the order of 10 S cm−2 at 973 K for ZMG232 alloy.